I am using #8 machine screws throughout the interior to hold the panels up. The clip nut in the pic is far superior to the aluminum tab/sheet metal screws Cessna used. I am doing my best to avoid those sheet metal screws wherever possible.

Notice the AV-30 on the stringer? it has remarkable penetration, This particular seam is also an outside skin overlap. The AV-30 clearly found it’s way to the outside edge and beyond. So far, I have been able to locate almost every screw with enough accuracy.

Take a look at the rear overhead panel. Plane Plastics makes it as a NON COMPOUND part. In other words it's flat from front to back. The  original panel fit the airframe (a compound curve) perfectly. So, in my attempt to make the panel fit and keep the much needed 3 inches  headroom, I designed a tool to "shrink" the plastic right behind the  access hole. I also cut the plastic forward of the access hole. Without  doing this, the panel would need very long screws, it would be very warped and it put major stress on the flap cable "guide", bending it out of shape. So, this was my fix. A call to Plane Plastics confirmed  my findings. They were nice enough to offer to replace the panel if I  messed it up. I can't say I'm proud of this mod, but it works.

Vantage Plane Plastics. What can I say about this subject without being  downright mean, hateful and nasty? Remember, Plane Plastics sells  FAA-PMA interior parts, simply remove and replace, then make a log book  entry. The good news is that the installed plastic IS nice looking,  slightly amateurish in appearance and it is "intact". Things the  original interior was not. It took 3 months of non stop work to make  the parts fit. I have many years of interior experience too, mostly on  high end jets, so I am capable of high quality work. To start with, the  parts don't fit. They are all too big, and not in a good way. It's not  a matter of trimming the edges. The rear window panels must fit inside the window opening. BUT, the plastic panel is 1/4 to 1/2 inch larger.  Plus the shape is such that trimming makes it bigger still (inward  tapered edges). NOT GOOD. The trim over the doors was a WHOPPING 6 inches off! The heat gun allows the plastic to be formed, but complex  shapes flatten out before it's hot enough to reshape! UGG!

I painted all the panels with a sand colored aircraft interior paint from Airtex. It goes on easily, it's easy to adjust texture and it dries in seconds (no bugs or grit). Plus, it's easy to touch up. I like  it.
 

The Airtex subject. The seats look very nice after the installation and I am pleased with them.  All the seats glue on to the frames except the front uppers, which  slide and velcro on. What's up with this? This gives a cheesy flat look to the seat backs, as they don't form fit the seats. However, just like the Vantage Plane Plastics company, the interior is an FAA-PMA interior, just a simple log book entry needed.

A word of warning about Airtex, the seat style is not the design we ordered, nor is the leather in the proper location. It seems they just made them however they felt like making them.  Repeated attempts at resolving the situation went unanswered, even after meeting with the company owner.

Bottom line: The end result is far better than what was removed.